Modulus Strain Research Articles

Analiza osnovnih mehaničkih svojstava mješavina recikliranog betona s recikliranim krupnozrnatnim agregatom

Three kinds of recycled aggregate concretes (RACs), with six different replacement rates at four ages, are subjected to the standard cube axial compression test to study mechanical properties. Failure modes, compressive strength, stress-strain curves, peak strain, and elastic modulus of RACs are systematically analysed. In addition, three equations are proposed for RACs to describe the relationship between the compressive strength and replacement rate. Comparison between various equations of elastic modulus and test results is presented, and then three most suitable equations are established for three kinds of RACs, including necessary modifications, especially for RAC with mixed recycled aggregates.

Constitutive model for ultra-high performance concrete (UHPC) considering the size effect under cyclic compressive loading

In this study, the size effect of the thickness of the specimen on the mechanical properties of UHPC was investigated through compression tests under cyclic loading. UHPC prisms with different thicknesses from 20 mm to 100 mm were tested under unloading/reloading cycles and the stress–strain curves were recorded for this purpose. A constitutive model to predict the stress–strain response of UHPC accounting for the thickness was proposed. It was found that UHPC specimens with different thicknesses showed the same failure mode of diagonal shear failure. The size effect of thickness was significant for the compressive strength but was negligible for the peak strain and elastic modulus. The damage of the unloading modulus and reloading modulus at zero stress only occurred when the unloading strain exceeded 0.8 times the peak strain. Furthermore, the proposed constitutive model could predict the stress–strain response for UHPC with different thicknesses under cyclic compressive loading with acceptable accuracy.

Springback behavior of a metal/polymer laminate in incremental sheet forming: stress/strain relaxation perspective

Metal/polymer laminates are important lightweight construction composite materials. In search of economical alternatives of expensive traditional processes, feasibility of Single Point Incremental Forming (SPIF) to process laminates is being analyzed nowadays. Poor accuracy is one of the major drawbacks of this innovative process. Therefore, the present study aims at investigating the accuracy and identifying the mechanism controlling the springback in SPIF of the laminates. The High-Density Polyethylene (HDPE) sheets of varying thickness are adhesively bonded to Al–1060H24 sheet to build metal/polymer laminates. These laminates and the constituting monolithic sheets are subjected to SPIF and relaxation tests to identify the relevant springback mechanism (s). The results reveal that the magnitude of relaxation modulus of the laminate interestingly decreases as the polymer-to-metal thickness ratio increases. As a result, agreeing with the mechanics intuition, stress relaxation increases but amazingly strain relaxation decreases due to metal/polymer intactness thereby resulting in reduced springback in the formed components. The monolithic polymer sheet on the contrary experiences an increase in the relaxation modulus upon increasing thickness resulting in decrement in both the stress and strain relaxations thereby causing reduction in the springback. From analysis of the property–error correlations, strain relaxation is identified as the main springback controlling property in the laminates. On the other hand, both the stress and strain relaxations and modulus are detected as the springback controlling properties in polymers. The laminates are witnessed to experience a way lower profile error than the polymer attributing to lower strain relaxation. `

Short-term vancomycin and buffer soaking does not change rabbit achilles tendon tensile material properties

BackgroundAllograft tendons are commonly used during orthopedic surgery to reconstruct tissue that is severely damaged. Soaking the tendon in an antibiotic solution, specifically vancomycin, has been shown to lower the risk of post-operative infections. While some material properties of tendon and ligament after antibiotic soaking have previously been characterized, extensive sub-failure allograft tendon material properties after soaking in antibiotic solutions have not. MethodsForty tendons were dissected from rabbits and soaked in either a phosphate buffered saline (PBS) only solution or vancomycin and PBS solution for five or 30 min. Immediately after soaking, quasi-static tensile experiments were performed in a materials testing system. FindingsTissue nominal stress, Lagrange strain, toe-region properties and elastic modulus were characterized. For all forty tendons, the average elastic modulus was found to be 455 ± 37 MPa, the average transition strain (from toe-region to linear elastic region) was 0.0487 ± 0.0035, and the average transition stress was 9.71 ± 0.79 MPa. No statistically significant differences in any of these material properties were found across soaking medium or soaking time. InterpretationFrom these results, we conclude that soaking an allograft tendon in antibiotic solution for up to 30 min prior to implantation does not change the tensile material properties of tendons, supporting current clinical practice.

Substrate-Free Thermoelectric 25 μm-Thick Ag2Se Films with High Flexibility and In-Plane zT of 0.5 at Room Temperature.

Thermoelectric inorganic films are flexible when sufficiently thin. By removing the substrate, that is, making them free-standing, the flexibility of thermoelectric films can be enhanced to the utmost extent. However, studies on the flexibility of free-standing thermoelectric inorganic films have not yet been reported. Herein, the high thermoelectric performance and flexibility of free-standing thermoelectric Ag2Se films are reported. Free-standing Ag2Se films with a thickness of 25.0 ± 3.9 μm exhibited an in-plane zT of 0.514 ± 0.060 at room temperature. These films exhibited superior flexibility compared to Ag2Se films constrained on a substrate. The flexibility of the Ag2Se films was systematically investigated in terms of bending strain, bending radius, thickness, and elastic modulus. Using free-standing Ag2Se films, a substrate-free, flexible thermoelectric generator was fabricated. The energy-harvesting capacity of the thermoelectric generator was also demonstrated.

Effect of l-cysteine and l-ascorbic acid addition on properties of meat analogues

Currently, studies are underway to use pea protein isolate (PPI) for the production of meat analogues because it is considered as a more sustainable alternative to soy. The potential of PPI has been demonstrated in extrusion and PPI in combination with wheat gluten has been studied in the shear cell. To enlarge the possibilities to make meat analogues with a broader range of properties, the effects of l -cysteine (CYS) and l -ascorbic acid (AA) on PPI and wheat gluten (WG) blends were examined at different concentrations (0, 100, 500, 1000 and 2000 ppm). The results showed that both CYS and AA altered the properties of the products formed by the high-temperature shear cell (HTSC). Both additives altered the fibrousness and the mechanical properties of the products obtained after processing. Especially CYS revealed an increase in tensile stress, tensile strain and Young's modulus as its concentration increased. However, products containing CYS depicted a relatively stable anisotropic index of 1, which corresponded to a densely packed matrix that was observed by microstructural analysis. A small elevated anisotropic index (>1) of products containing AA at concentrations of 500–2000 ppm could be attributed to the formation of pores parallel to the shear flow direction in these samples visualized by a confocal laser scanning microscope (CLSM) and the scanning electron microscope (SEM). In the products containing 2000 ppm of AA and 2000 ppm CYS, small and large fibers were formed, respectively. Therefore, this research pointed out the potential application of CYS and AA to alter and control the textural attributes of products. This application could aid in improving the consumer acceptance of meat analogues and, thus, contribute to being able to feed the increasing population of the world. • l -cysteine and l -ascorbic acid were examined for the production of meat analogue. • They altered properties of products formed by high-temperature shear cell. • l -cysteine increased tensile stress, tensile strain and Young's modulus of products. • l -ascorbic acid increased the browning index, fiber formation and anisotropy index.

Analysis of Stress, Strain and Young's Modulus of Specimens under Propagation of the 1D Linear Elastic Stress Waves

Analysis of Stress, Strain and Young's Modulus of Specimens under Propagation of the 1D Linear Elastic Stress Waves

Tensile Properties and Prediction Model of Recombinant Bamboo at Different Temperatures

The destruction of recombinant bamboo depends on many factors, and the complex ambient temperature is an important factor affecting its basic mechanical properties. To investigate the failure mechanism and stress–strain relationship of recombinant bamboo at different temperatures, eighteen tensile specimens of recombinant bamboo were tested. The results showed that with increasing ambient temperature, the typical failure modes of recombinant bamboo were flush fracture, toothed failure, and serrated failure. The ultimate tensile strength, ultimate strain and elastic modulus of recombinant bamboo decreased with increasing temperature, and the ultimate tensile stress decreased from 154.07 to 96.55 MPa, a decrease of 37.33%, and the ultimate strain decreased from 0.011 to 0.008, a decrease of 26.57%. Based on the Ramberg-Osgood model and the pseudo‒elastic design method, a predictive model was established for the tensile stress–strain relationship of recombinant bamboo considering the temperature level. The model can accurately evaluate the tensile stress–strain relationship of recombinant bamboo under different temperature conditions.

M-mode and tissue doppler estimation of age and gender-specific normative values of aortic stiffness in healthy adults

Background:The elastic properties of the aorta are modified in numerous cardiovascular (CV) and non-cardiovascular (non-CV) diseases. Multiple studies have evaluated aortic stiffness in myriads of disease state, albeit only a few Indian studies have estimated the normal values of aortic stiffness in the healthy population. Objective: To the best of our knowledge, till date, no research has been undertaken to determine the age and gender-specific value ranges of aortic stiffness parameters in healthy subjects. Hence, in the present study, we endeavored to estimate these values in our distinctive study groups of healthy adults. Methodology: This was a prospective observational study in which 58 healthy adults were enrolled during the turbulent Corona pandemic. The study group consisted of individuals of either sex within the age range of 18 to 60 years and was divided into six groups arbitrarily. Exhaustive M-mode and Tissue Doppler Imaging (TDI) was performed by a 4-dimensional XStrain echocardiography (4D XStrain E) system for extensive evaluation of multiple M-mode and TDI-derived parameters of aortic stiffness and superior wall velocities of ascending aorta. Result: Aortic Systolic diameter (AOS), Aortic Diastolic diameter (AOD), aortic strain, and elasticity modulus were greater in males. On the contrary aortic superior wall velocities (SAO: Aortic superior wall velocity, EAO: Early diastolic velocity, and AAO: Late diastole velocity) were higher in females. Increasing age leads to a decline in the majority of stiffness parameters derived by M-mode echocardiography. Correspondingly, EAO showed a deterioration with advancing age. Conclusion: The authors report a normal range of M-mode and TDI-derived values of aortic stiffness of ascending aorta in healthy Indian adults. The difference in magnitude of aortic elasticity indices has been demonstrated in men and women, as well as in different subsets of the study group.

Mechanical characteristics and failure behavior of puckered and buckled allotropes of antimonene nanotubes: a molecular dynamics study.

In recent years, antimonene nanotubes have attracted considerable interest for diverse applications owing to their promising physical properties. In this study, classical molecular dynamics simulations with Stillinger-Weber potential were carried out to explore the fundamental mechanical characteristics of two stable allotropes of antimonene nanotubes (SbNTs), namely puckered (α-) and buckled (β-) nanotubes. Mechanical properties and deformation mechanisms of antimonene nanotubes, including ultimate tensile strength, fracture strain, and Young's modulus, were thoroughly examined by considering chirality, diameter, temperature, and strain rate variables. Numerical simulations revealed that all SbNT specimens examined in this study exhibit brittle failures with a complete loss of load-bearing capability following the ultimate stress level. The brittle nature of the SbNTs with varied diameters remained unchanged under different temperatures and loading-rate conditions. Owing to their distinct crystal structure in the armchair and zigzag directions, α-SbNTs present a distinctive anisotropic behavior compared to β-SbNTs. While the variation of the elastic modulus with temperature is not notable, the tensile strength and fracture strain of SbNTs deteriorated considerably at high temperatures. Furthermore, it was observed that the effects of diameter and temperature on zigzag α-SbNT are more pronounced due to its lower stability. Altogether, this study presents a comprehensive examination of the mechanical characteristics of the two stable antimonene allotropes and provides useful information for their potential utilizations in a wide range of applications.

Investigation of structure and properties of melt-spun NiTi based shape memory alloys

In this work, we investigated the structure, mechanical properties and corrosion resistance of Ti50Ni50 and Ti16.667Zr16.667A16.667Ni25Cu25 (A = Hf, Nb, Co, Cr and Ga) shape memory alloys (SMAs) fabricated by using melt-spinning method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses reveal that the alloy ribbons are partially crystallized with B19' martensitic structure in the added alloys. The crystalline phase formation and the atomic size difference (δ = 4.33 - 10.25%) significantly affect the hardness, tensile strength, tensile strain, elastic modulus and corrosion resistance of the alloys. The hardness of the alloy gradually increases from 583 HV to 873 HV when adding elements in the order of Hf, Nb, Co, Cr and Ga. Tensile strength, tensile strain and elastic modulus simultaneously reach their maximum of 669.2 MPa, 0.899% and 28.82 GPa, respectively, when Hf is added to the alloy. Ga enhances the corrosion resistance of the alloy ribbons more than other additional elements.

Mechanical performance of composites reinforced with carbon black and different types of graphitic nanofillers for different applications

The piezo-electric energy harvesting devices based on rubber composites have attracted great attention in the field of flexible electronics. These devices have the ability to provide a voltage of ∼0.5 V when subjected to mechanical strain. In this work, carbon allotropes nanofillers were used to reinforce the room-temperature vulcanized silicone rubber (RTV-SR). The nanofillers added to the rubber matrix were found to improve the compressive modulus, tensile strength, fracture strain, and tensile modulus. For example, the compressive modulus was 1.29 MPa (Virgin) and improved to 1.4 MPa (graphene), 2.3 MPa (CB), 2.2 MPa (CB–graphite hybrid), 2.17 MPa (CB–Nano graphite hybrid), and finally 2.19 MPa (CB–graphene hybrid). Similarly, the fracture strain was 146% (Virgin) and improved to 149% (graphene), 156% (CB), 160% (CB–graphite hybrid), 151% (CB–Nano graphite hybrid), and lastly 178% (CB–graphene hybrid). Moreover, the effect of three different diameters of loading tips is used for voltage production. More areas of deformation during energy harvesting can be able to produce higher voltage output. For example, a 21 mm tip can produce higher energy output than 7 mm and 14 mm. In the end, it was found that formation of cracks in the electrode while repeated loading causes a reduction in voltage output.

Microstructural analysis, physical, chemical components and tensile properties of coir fibre long-term exposed in Ca(OH)2 as representative of concrete pore solution

In this study, the microstructure, chemical composition, linear density, tensile modulus of elasticity, tensile strength and strain at break of coir fibres exposed to saturated Ca(OH)2 solution (i.e., pH = 12.5) up to 24 weeks were investigated. Different fibre surface modification methods were applied on coir fibres to investigate their effectiveness on the long-term tensile performance of coir fibres. The surface modification methods included treating fibres in: (1) boiling water, (2) 0.01 g/ml NaOH solution, or (3) 5% H2O2 solutions for 2 h, respectively. Coir fibres after modifications were then immersed in Ca(OH)2 solution up to 12 weeks and tested in tension at time intervals of 0, 4 and 12 weeks, respectively. Coir fibres without surface treatment were also immersed in both Ca(OH)2 solution and distilled water up to 24 weeks and tested in tension at intervals of 0, 2, 4, 12 and 24 weeks, respectively. Statistical significance test was used to discuss the change in the fibre linear density and tensile properties. The results showed that all the surface modifications selected had no significant influence on the linear density of coir fibres. Thermogravimetric analysis and Fourier-transform infrared spectroscopy confirmed the decomposition of hemicellulose of coir fibres and the generation of CaCO3 on the fibre surface after exposure to Ca(OH)2 solution. The average tensile strength of the coir fibre reduced to 74% and 66% respectively after 12 and 24 weeks exposure in the Ca(OH)2 solution in comparison with that of fibre exposed in distilled water. The corresponding average ultimate strain also reduced to 53% and 27% at 12 and 24 weeks. No obvious tendency could be identified in the average tensile E-modulus of coir fibre after long-term exposure. Through scanning electron microscopy, it was found that failure along the microfibrils and tensile failure of the microfibrils were the two main failure modes of coir fibre under tension. Surface modification with NaOH changed the permeability of coir fibre surface. Tylosis decomposition occurred due to H2O2 solution modification. Neither H2O2 solutions nor boiling water modification had significant influence on the tensile behaviour of coir fibre.

Effects of single-phase and Co-deposited interphases on mechanical hysteresis behavior in T700TM mini-Cf/SiC composites

Hysteresis behavior in Cf/SiC composites is affected by the interface properties. The objective of this paper is to establish the relationship between the mechanical hysteresis behavior of mini-Cf/SiC composites and interphase type (i.e., single-phase PyC interphase and co-deposited (PyC + SiC) interphase) and thickness (i.e., 300 ∼ 2000 nm). Cyclic tensile loading/unloading experiments were conducted for different mini-Cf/SiC composites. Evolution of composite’s cyclic strain, hysteresis width, and secant modulus with increasing peak stress were analyzed. The composite’s thermal residual stress (TRS) was obtained through the common intersection compliance point (CIP) method. Micro damage mechanisms of surface cracking in the matrix and fiber’s pullout at the fracture surface were observed under the SEM to characterize composite’s internal damage state. A micromechanical first loading–unloading-reloading constitutive model was developed to predict cyclic mechanical response. The values of interface slip ratio (ISR) and interface shear stress (ISS) were obtained through the hysteresis analysis. For the same interphase thickness and similar fiber volume of PyC and (PyC + SiC) interphase, the ultimate tensile strength (UTS) of mini-Cf/SiC composites with the PyC interphase was higher than that of the samples with the (PyC + SiC) interphase. The values of ISS for the mini-Cf/SiC with the (PyC + SiC) interphase were much higher than those of mini-Cf/SiC with PyC interphase.

DEM study on the macro- and micromechanical behaviours of breakable granular materials under cyclic loading

The effect of cyclic loading on the macro- and micromechanical behaviours of breakable granular materials was investigated via DEM. Breakable particle models composed of Voronoi cells with realistic shapes were constructed. A series of confined cyclic loading tests were performed at different loading amplitudes. The macroscopic deformation behaviours were investigated in terms of the cumulative plastic strain and dynamic resilience modulus. Then, particle breakage characteristics, including the extent of particle breakage, crack orientation distribution, breakage pattern and correlation between the particle breakage and energy input, were explored. Furthermore, micromechanical results, including the coordination number, sliding contact and contact orientation anisotropy, were examined. It is found that both particle breakage and cumulative plastic strain increase rapidly in the early stage of loading. In the stable state, both showed an S-shaped increase with increasing loading amplitude. This study highlights that particle breakage is one of the main sources of permanent deformation.

Strain-induced control of radiative heat transfer between nanoparticles in a plasmonic cavity

Graphene enables the versatile modulation and significant enhancement of their optical properties by external strains, which plays a pivotal role in various applications, such as active thermal modulation. In this work, we investigate the near-field radiative heat transfer (NFRHT) between two nanoparticles mediated by a strain-induced plasmonic cavity consisting of the two parallel graphene sheets (GSs) under external mechanical strain. By adjusting the strain modulus, the ellipsoidal surface plasmon polaritons supported by strain-induced graphene are found to significantly impact the NFRHT between nanoparticles. The integral and interlayer twist can synergistically manipulate the reflection properties of the cavity, allowing the anisotropic coupling of nanoparticles with the cavity in different directions. Under large strain modulus and suitable twisted angles, the NFRHT can be enhanced up to 5 orders of magnitude. In addition, the chemical potential of graphene can be tuned to provide additional ways to modulate the heat transfer between nanoparticles. These findings may open up promising avenues for highly efficient thermal management, thermal communication, and energy harvesting.

Predicting stress-strain behavior of normal weight and lightweight aggregate concrete exposed to high temperature using LSTM recurrent neural network

Lightweight aggregate is commonly used to reduce the self-weight of concrete elements which can efficiently mitigate the environmental impact. This study investigates the mechanical performance of normal weight aggregate concrete (NWAC) and Lightweight aggregate concrete (LWAC) exposed to high temperature, focusing on developing a predictive model for the stress-strain relationship of the LWAC based on the property of cement, silica fume, light weight aggregate and water/cement ratio. Mechanical properties of 30 different mixtures, including uniaxial compressive stress–strain relationship, compressive strength, modulus of elasticity, and failure strain are determined before and after high temperature exposures at 250, 500, and 750 °C. Results show that the modulus of elasticity and compressive strength of LWAC increased with exposure temperature. In particular, mixture S4 was found to outperform other mixtures, which retained 96, 75, and 46 % of compressive strength following exposures to 250, 500, and 750 °C, respectively. At all the temperatures investigated, the specimens of this mixture were able to achieve satisfactory modulus of elasticity and maximum strain. The specimens prepared with mixtures containing 75 % LECA (S23) showed a higher retention compressive strength at 750 °C. This study also utilizes the long short-term memory (LSTM) neural network to predict the stress-strain relationship of NWAC and LWAC mixtures after exposure to high temperatures. The results show that the LSTM model could adequately predict the stress-strain relationship of both LWAC and NWAC mixtures in terms of compressive strength, modulus of elasticity, and failure strain at elevated temperatures.

Mechanical and Microscopic Properties of Copper-contaminated Soil Solidified with Calcium Carbide Residue, Metakaolin, and Desulfurization Gypsum under Freeze-thaw Cycles

The solidification/stabilization effect of heavy metal contaminated soils in frozen soil regions may be weakened. A novel binder comprising calcium carbide residue, metakaolin, and desulfurization gypsum was used to solidify and stabilize copper-contaminated soil subjected to freeze-thaw (F-T) cycles. The unconfined compressive strength (UCS), F-T cycles, scanning electron microscope (SEM), X-ray diffraction (XRD), and pH tests were conducted to investigate the characteristics of UCS, deformation, pH value, and microscopic mechanism of contaminated soils. The results demonstrated that the UCS of contaminated soils decreased with the increasing F-T cycles and Cu2+ concentration; the strength loss rate increased first and then decreased as the F-T cycles increased. The failure strain rose first and then reduced with the increase of F-T cycles, and increased with the rise of Cu2+ concentration. There was a considerable correlation between UCS, failure strain, and deformation modulus E50. The pH value decreased with the increasing F-T cycles and Cu2+ concentration. The microscopic characteristics indicated that the formation of hydrated calcium silicate and ettringite was the fundamental reason for the enhanced UCS. Besides, heavy metals could be solidified and stabilized by chemical precipitation, physical encapsulation, and ion exchange. The effect of F-T cycles could significantly damage the internal structure of contaminated soils, and the frost heaving force could loosen the soil skeleton structure, leading to the deterioration of the mechanical properties.

Bearing Capacity of Forest Roads on Poor-Bearing Road Subgrades following Six Years of Use

The research was conducted on a forest road on the territory of the State Forests in Poland, in the Brzeziny Forest District, where eight test sections with a total length of 422 m were created with different pavement system on a low-bearing soil substrate (clay, silt loam) as part of the road reconstruction in 2016. The bearing capacity of the pavement was evaluated based on the static strain modulus ME MN·m−2 by measuring with a statistic plate (VSS), the dynamic deformation modulus Evd MN·m−2 obtained from lightweight deflectometer measurements, and the elastic deflection of the pavement Us mm evaluated from Benkelaman beam measurements. It has been shown that pavements made of crushed aggregate and common gravel on timber roller substructure maintain good bearing capacity parameters, where the average values of secondary modulus of strain are above 130 MN·m−2, and in the case of pine rollers, this modulus has increased. Pavements on low-bearing soils reinforced with willow brushwood mattresses have low bearing capacity parameters, with averages of 26.09 ≤ MEII ≤ 53.93 and 22.1 ≤ Evd ≤ 39.1 MN·m−2, but the technical condition of the pavement makes it possible to continue carrying out forestry-related transportation. The research confirms the possibility of reinforcing soils with poor bearing capacity with wooden rollers, and in the case of willow mats for roads with light truck movements.

Mechanical properties and microstructural evolution of FeNiCrCoCux high-entropy alloys: A molecular dynamics simulation

In this work, we used molecular dynamics simulations to research the relationship between mechanical properties and microstructural evolution in FeNiCrCoCux high-entropy alloys under uniaxial tension. The physical models were constructed based on the atomic simulations. We considered the influencing factors of Cu concentration (x = 0.1, 0.5, 1.0, 1.5, 2.0), temperature (300–1200 K) and strain rate (1 × 108–1 × 1011/s). The analysis of the results revealed multiple deformation mechanisms such as dislocation movement and shear strain. Both Cu concentration and temperature increase negatively affect the tensile properties of HEAs, including yield stress, yield strain, and Young's modulus. The dislocation density will thus decrease, and the shear strain will increase and become more uniform. The increase in strain rate increases the yield stress and yield strain of HEAs, while the change in Young's modulus is smaller and the dislocation density generally decreases. This work provides a microscopic understanding. We can design HEA with excellent mechanical properties by optimizing the material structure parameters of HEA.